On-fault earthquake energy density partitioning from shocked garnet in an exhumed seismic midcrustal fault

The energy released during an earthquake is mostly dissipated in the fault zone and subordinately as radiated seismic waves. The on-fault energy budget is partitioned into frictional heat, generation of new grain surface by microfracturing, and crystal-lattice distortion associated with dislocation defects. The relative contribution of these components is debated and difficult to assess, but this energy partitioning strongly influences earthquake mechanics. We use high-resolution scanning-electron-microscopy techniques, especially to analyze shocked garnet in a fault wall-rock, to provide the first estimate of all three energy components for a seismic fault patch exhumed from midcrustal conditions. Fault single-jerk seismicity is recorded by the presence of pristine quenched frictional melt. The estimated value of energy per unit fault surface is ~13 megajoules per square meter for heat, which is predominant with respect to both surface energy (up to 0.29 megajoules per square meter) and energy associated with crystal lattice distortion (0.02 megajoules per square meter).


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Figs. S1 to S8      Stress components calculated for a fracture propagating at a velocity corresponding to 0.9 of the shear wave velocity, close to Rayleigh velocity (0.92 of the shear wave velocity) in a material with elastic properties typical of middle-crustal felsic rocks (see Methods).Calculations are performed in a reference frame moving with the tip of the fracture and in a fixed frame.(A), maximum principal stress, minimum principal stress and shear stress around the tip of a propagating fracture.The interval of stress contours is 1.5 GPa.(B), Stress plotted as function of time at a fixed point located at a distance of 3 mm (above, Y>0, and below, Y<0) from the rupture surface during fracture propagation.At t = 0 s, the fracture tip is at the shortest distance from the fixed point; the fracture tip is approaching the point and proceeding away from it at negative and positive values, respectively.

Fig. S8. Mean angular error (MAE) and high-resolution kernel average misorientation (HR-KAM).
MAE is a parameter useful to evaluate the quality of the cross correlation.Only points with MAE below 0.2292° are considered reliable for the analysis.HR-KAM, calculated in every pixel as the average misorientation with respect to the surrounding pixels, is useful to visualize the noise contribution in the analysis.

Fig. S2 .
Fig. S2.High-angular resolution electron backscattered (HR-EBSD) maps locations.(A), Visible light image of the investigated garnets.Red squares mark the locations of the EBSD maps.(B, D, F), Band-contrast EBSD maps.Red squares mark the locations of the five HR-EBSD maps.(C, E, G), EBSD maps color-coded by crystal orientation according to the inverse pole figure inset in the bottom-right corner of (C) with respect to the Z direction

Fig. S3 .
Fig. S3.Probability distribution and distribution form analysis of the stress heterogeneities for   and   .(A), probability distribution.(B), normalized probability distribution.(C), restricted second moment of the probability distribution

Fig. S6 .
Fig. S6.Clast-size distribution graphs.Log-log graphs with equivalent radius in x-axis and cumulative number of clasts per class on the y-axis.Interpolating segments are represented with the respective D-values and R-squared fitting parameters.

Fig. S7 .
Fig. S7.Stress field surrounding the tip of a mode II propagating fracture.Stress components calculated for a fracture propagating at a velocity corresponding to 0.9 of the shear wave velocity, close to Rayleigh velocity (0.92 of the shear wave velocity) in a material with elastic properties typical of middle-crustal felsic rocks (see Methods).Calculations are performed in a reference frame moving with the tip of the fracture and in a fixed frame.(A), maximum principal stress, minimum principal stress and shear stress around the tip of a propagating fracture.The interval of stress contours is 1.5 GPa.(B), Stress plotted as function of time at a fixed point located at a distance of 3 mm (above, Y>0, and below, Y<0) from the rupture surface during fracture propagation.At t = 0 s, the fracture tip is at the shortest distance from the fixed point; the fracture tip is approaching the point and proceeding away from it at negative and positive values, respectively.